add comments to suppres -Wimplicit-fallthrough warnings

Origin commit data
------------------
Commit: 0ea72b9d51
Author: Stefan Seyfried <seife@tuxbox-git.slipkontur.de>
Date: 2017-09-25 (Mon, 25 Sep 2017)

lib/jsoncpp/jsoncpp.cpp

@@ -1455,6 +1455,7 @@ bool OurReader::readToken(Token& token) {
     ok = readStringSingleQuote();
     break;
     } // else continue
+    /* is a break missing here? or is this correct? */
   case '/':
     token.type_ = tokenComment;
     ok = readComment();